Car Craft
Click here to find out more!

Chevy Chevelle Bolt-on Suspension Performance Test - Find The Handle

Not Everybody Needs The Latest In High-Tech Suspension Technology, So We Thought We'd Take A Look At Some Simple Mods That Can Help Almost Any Muscle Car . . .

By , Photography by Brian Cox, , ,

If you own a muscle car, it's hard to avoid all the superlatives bouncing around the industry about custom tube chassis, adjustable shock absorbers, and the latest bumpsteer drama that seem to have taken on the intensity of a well-orchestrated soap opera. Mired in this jungle of information is some basic information that can help the entry-level suspension tuner make some simple changes that can turn your sleepy '60s muscle car into a much more stable machine that could completely change your opinion of older cars. Our willing participant, Brian Cox, purchased his '67 Chevelle a couple of years ago but soon discovered that the car lacked finesse when it came time to change lanes on the freeway, so he was looking to improve its agility and steering response.

The good news is that a couple of bolt-on parts can make a world of difference, and that's the Car Craft way of doing things. When it comes to the front suspension on all '64 through '72 Chevelles, the car suffers from multiple weak points. In no particular order, these include stupid-soft front coil springs, piano wire that doubles as a front sway bar, and an aggressively poor camber curve. This terrible camber exercise is dictated by a short spindle height that creates an increase in positive camber anytime the front springs are compressed with body roll. Since body roll is accentuated by cushy springs and a small antiroll bar, attending to these parts is one of the easiest and quickest ways to improve handling on these early Chevelles and Camaros.

Decades ago, when there were not a lot of aftermarket parts available for these cars, the early Chevelle handling pioneers discovered that the second-generation ('70-'81) F-body front sway bar bolts right up to an early Chevelle. Many second-generation Camaros and Firebirds used stock 1 1/8-inch front sway bars that really helped control body roll on early Chevelles. While the chances of finding a '70 Firebird in the boneyard today is remote, companies such as Addco have the front (and rear) bars you need sitting on the shelf. Cox wanted to complement the sway bars with a set of shocks that would be affordable and improve handling but not ruin the ride quality. Before all the hero moves, however, his first step was to completely restore the stock front suspension with an OPG rebuild kit with new ball joints, control arm bushings, and a new drag link. Once that was accomplished, Cox landed a set of Bilstein shocks from Race Car Dynamics (RCD) that are much more than just painted Bilstein shocks. RCD tunes these shocks to work more effectively on a Chevelle to deliver decent ride quality and an improvement in suspension control.

Finally, we know one of the best ways to improve handling is to go right to the interface between the suspension and the road: the tires. Cox's choice of rolling stock for the Chevelle revolved around set of traditional 15-inch Cragars and BFGoodrich Radial T/A tires. Though that combination is timeless, we proposed something a little more aggressive with an upgrade to a set of 17-inch Center Line wheels and General Exclaim UHP Grabber tires. With a set of 17x8-inch wheels, we mounted a pair of 255/40R17s on the front and slightly larger 275s on the rear. With that, we were ready to test.

The Bolt-Ons
Improving the handling on a Chevelle doesn't get much easier than spending about an hour bolting on a set of shocks to complement the front and rear sway bars. Cox came up with a stainless 5/16-inch ARP stud with a large washer and nut inside the frame and a 3/8-hex 12-point stainless nut on the outside to secure the polyurethane bushing. This is an upgrade because just a bolt alone through the frame will often pull out due to the increased load on the threads. A stud, washer, and nut on the inside of the frame dramatically increases the load capacity.

The original factory rear sway bar bolts on to the lower control arms. Cox upgraded to a pair of OPG stock style boxed lower arms. Another option would be to add a pair of Global West or Hotchkis tubular lower control arms. One advantage to the tubular arms is they are generally stiffer and do not allow the body to move laterally over the rear axle. This is especially important when fitting larger rear tires where clearance is minimal.

The Test
When it came time to do our testing, we humped it down to the ex-El Toro Marine Corps air station, using the huge concrete runway where F-4 Phantoms and A-4 Skyhawks used to take off during the '60s. Camaro Performers Editor Nick Licata and Steven Rupp helped us with the testing with Nick doing the driving. Our test procedure was to run the modified suspension with the 15-inch tires first, then try the 17s, then retain the 17s after converting to the old shocks and sway bar, and finally testing the old suspension with the 15-inch tires to evaluate the effects of the addition of the tires alone.

DESCRIPTION 420-FOOT SLALOM
SLALOM
AVERAGE SPEED (MPH) BEST SPEED (MPH) AVERAGE (G-FORCE) BEST (G-FORCE)
Test 1: old suspension, 15-inch tires 41.27 42.68 0.76 0.77
Test 2: old suspension, 17-inch tires 41.57 (+0.30) 44.62 (+1.94) 0.79 (+0.03) 0.81 (+0.04)
Test 3: new suspension, 15-inch tires 42.31 (+1.04) 43.20 (+0.52) 0.79 (+0.03) 0.82 (+0.05)
Test 4: new suspension, 17-inch tires 43.93 (+2.66) 44.62 (+1.94) 0.81 (+0.05) 0.83 (+0.06)
Note: All improvements (in parenthesis) are measured against Test 1.

Performance Evaluations
We have to spend some time with the results chart so it is not misleading. If we only look at the peak slalom speeds, the peaks appear to suggest that the new suspension parts produced little or no improvement. That's why we included the average numbers. While the peak numbers lend some insight into what the suspension and/or tires are capable of producing, the average numbers reveal much more. Overall, we saw a significant improvement in average speed on the slalom of just over 1 mph with the addition of the sway bars and shocks, but a better indicator was the increase in average speed when the 17-inch tires and wheels were added to the suspension in Test 4.

The best way to learn more from these numbers is to subtract the average speeds from the best speeds to evaluate how difficult the car was to drive. It makes sense that the closer the average speed is to the peak, the easier the car is to drive. Conversely, the wider the gap between the two numbers, the harder the car is to drive. Using this evaluation, the old suspension with the 17-inch tires (Test 2) reveals a massive discrepancy of 3.05 mph (44.62 - 41.57 = 3.05 mph), while the smallest difference between peak and average was with the new suspension with the 17-inch tires (44.62 - 43.93 = 0.69 mph). So while Licata was able to bang out a great time with the 17-inch tires on the old suspension, it was a hero effort that he was not able to replicate in five other attempts. On average, he was much smoother and the car was far easier to drive with the Bilstein shocks and Addco sway bars along with the 17-inch General tires. This is no big surprise, but the numbers do tell an interesting story.

Skip pad testing must also be carefully evaluated. While we recorded a slight improvement in the lateral traction, the results were less than impressive because the majority of the increase came from the better tires. You can see this just by comparing the gain in Test 2 with Test 4. The explanation is also relatively simple: By design, the skid pad tests the suspension once it is completely loaded. That means this is really a test of suspension geometry, springs, and tire adhesion with virtually no input from the shocks. Since the springs are still stock and extremely soft, it's no surprise there were minimal gains.

The Next Level
If you've been reading Car Craft for a while, it should be no surprise that we've been beating on Chevelles to improve handling for many years. Along the way, we've learned much about what works and what doesn't. Condensing all this information would probably demand a book, but let's see how far we can get. In the front suspension, the limitation is the Chevelle's very short spindle height. As the body rolls, the stock geometry allows the loaded tire (the left front in a hard righthand turn, for example) to roll the top of the tire outward. This results in a major gain in positive camber-the exact opposite of what you would prefer the camber to do. The simple fix is to use monster-stiff springs in the front to limit body roll along with adding a couple of degrees of negative camber so when the body does roll, the positive camber gain will retain some negative camber to plant the loaded tire. But for a street car, all that negative camber is undesirable because it kills the inside edge of the front tires very quickly.

Many years ago, A-body suspension pioneers discovered that taller, '70-'81 Camaro or B-body (big-car) spindles bolt in place and radically alter the camber curve, so as the body rolls in a turn, negative camber actually increases allowing the suspension tuner to use street-friendly camber alignment settings. This eventually led to companies like Global West and Hotchkis building bolt-on tubular upper control arms that allow you to take full advantage of these taller spindles. A combination of calibrated front spring rates, tall front spindles, a pair of tubular upper control arms, and the proper sway bar will transform the front suspension in these cars.

That is exactly what we did with our '65 Chevelle several years ago and (with some minor changes) is the combination we used on it for the Run to the Coast event ("Pro Touring Shootout," Aug. '10). It's been a while since we tested the Chevelle on the skid pad, but with good tires, the car is capable of generating 1.0-plus g numbers. It also requires tubular upper and lower control arms in the rear and the elimination of the rear sway bar combined with a very soft spring rate. Of course, these performance numbers are assisted by big 275/40R17 or 275/35R18 sticky tires mounted on 17- or 18x9 1/2-inch wheels with 6 inches of backspacing front and rear. And yes, that tire and wheel package will fit under a '64-'67 Chevelle with very minor outer wheel lip trimming. We won't mislead you-generating this level of handling requires serious suspension tuning. But it is more time-consuming than difficult. The promising thing is that it can all be accomplished with a stock frame and stock suspension pickup points. If we can do it, you can, too.

PARTS LIST
DESCRIPTION PN SOURCE PRICE
Addco 1 1/8-inch front bar 883 Summit Racing $161.15
Addco 1 1/4-inch front bar 709 Summit Racing 172.97
Addco tubular 1 3/8-inch front 2278 Summit Racing 215.95
Addco 7/8-inch rear bar 692 Summit Racing 150.92
Addco 1-inch rear bar 690 Summit Racing 159.90
Addco front endlink kit 016 Summit Racing 11.37
RCR Bilstein front shocks 55-RO21 RCR
RCR Bilstein rear shocks 55-RO22 RCR
OPG front end rebuild kit RK-1004 OPG 239.95
OPG center link DS749 OPG 119.95
OPG rear lower arms KR00445 OPG 188.95
General UHP Grabber tires 245/45ZR17 Summit Racing 139.95
General UHP Grabber tires 275/40ZR17 Summit Racing 149.95 ea.
Center Line Wheels 7217805547 Center Line 249.00 ea.
Global tubular lower arms TBC-18 Global West 345.53
ARP stainless studs 400-2401 Summit Racing 21.95

SOURCES
Hotchkis Performance
12035 Burke Street
Suite 13
Santa Fe Springs
CA  90670
877-735-6425
http://www.hotchkis.net
Original Parts Group Inc. (OPGI)
1770 Saturn Way
Seal Beach
CA  90740
800-243-8355
www.opgi.com
Summit Racing Equipment
PO Box 909
Akron
OH  44398
800-230-3030
330-630-0240
www.summitracing.com
ADDCO Manufacturing
1596 Linville Falls Hwy
Linville
NC  28646
800-621-8916
http://www.addco.net
Race Car Dynamics, Inc.
1900 Weld Blvd
El Cajon
CA  92020
619-588-4723
www.racecardynamics.com
Flip's Tire Center
Van Nuys
CA
818-786-8686
www.flipstires.com
Global West Suspension
655 S. Lincoln Ave.
San Bernardino
CA  92408
877-470-2975
909-890-0759
http://www.globalwest.net
  • «
  • |
  • 1
  • |
  • 2
  • |
  • 3
  • |
  • View Full Article
Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!
0 comments
Car Craft